1. Field of the Invention:
This invention relates in general to printing presses, and in particular to an apparatus for preventing contact of wet ink on printed sheets with the printing press chain delivery mechanisms and for drying the wet ink on said printed sheets.
2. Description of the Prior Art:
In printing presses with chain delivery mechanisms, the sheet is drawn between a blanket cylinder and an impression cylinder, then gripped by a chain delivery mechanism and pulled rearwardly where it is deposited in a stack. The chain delivery mechanism has a pair of sprockets mounted next to the impression cylinder. A chain extends around each of the sprockets and has horizontal upper and lower runs. A gripping mechanism is mounted to the chains for gripping the leading edge of the sheet as it passes through the impression cylinder. The sprockets are mounted on a shaft that is parallel with the axis of the impression cylinder.
A long standing problem is avoiding contact of the wet ink on the sheets with the shaft that extends between the two sprockets. Any contact of the shaft with the ink will likely cause smearing. One system to avoid smearing comprises placing small wheels on the shaft. There are several different wheel designs. The wheels are preferably positioned to contact the sheet where no ink is deposited. This is not always possible. In sheets with an extensive amount of ink coverage, the wheels will contact the ink and cause smearing. Other devices have been proposed and used but not entirely satisfactorily.
Another long standing problem is that the ink is often still wet when the printed sheets are stacked. To prevent smearing at this stage, a drying powder is applied to the printed sheets. When more than one printing run is required, this powder can gum up in the printing press, causing delay, requiring maintenance, and jeopardizing the quality of the finished product.